如何画很多图像点?


小弟最近在学习图像处理,有个问题想请教下,如果知道一个StringList有很多座标点,如式如下:
60,10
61,10
62,10
55,11
53.11
.....如何根据这些座标点,在Image里画出这些黑色的点?
为什么我的代码没有生成点?
var
ImagePoint1: TStringList; // 记录图片点集合;
procedure TLocTestForm.BitBtn8Click(Sender: TObject);
var
    i,j:Integer;
    x,y,z:Integer;
begin    Image2.Width:=Image1.Width;
    Image2.Height:=Image1.Height;    for i := 0 to ImagePoint1.Count - 1 do
    begin
        z:=Pos(',',ImagePoint1.Strings[i]);
        x:=StrToInt(copy(ImagePoint1.Strings[i],0,z-1));
        y:=StrToInt(copy(ImagePoint1.Strings[i],z+1,Length(ImagePoint1.Strings[i])-z));        with Image2.Canvas do
        begin
            Pen.Color := clGreen;
            MoveTo(x,y);
            LineTo(x,y);        end;    end;
    Image2.Refresh;end;